diff --git a/artiq/compiler/transforms/inferencer.py b/artiq/compiler/transforms/inferencer.py
index a8b87491a..3fe2972b2 100644
--- a/artiq/compiler/transforms/inferencer.py
+++ b/artiq/compiler/transforms/inferencer.py
@@ -145,6 +145,8 @@ class Inferencer(algorithm.Visitor):
 
     def visit_IfExpT(self, node):
         self.generic_visit(node)
+        self._unify(node.test.type, builtins.TBool(),
+                    node.test.loc, None)
         self._unify(node.body.type, node.orelse.type,
                     node.body.loc, node.orelse.loc)
         self._unify(node.type, node.body.type,
@@ -788,6 +790,11 @@ class Inferencer(algorithm.Visitor):
 
             node.value = self._coerce_one(value_type, node.value, other_node=node.target)
 
+    def visit_If(self, node):
+        self.generic_visit(node)
+        self._unify(node.test.type, builtins.TBool(),
+                    node.test.loc, None)
+
     def visit_For(self, node):
         old_in_loop, self.in_loop = self.in_loop, True
         self.generic_visit(node)
@@ -798,6 +805,8 @@ class Inferencer(algorithm.Visitor):
         old_in_loop, self.in_loop = self.in_loop, True
         self.generic_visit(node)
         self.in_loop = old_in_loop
+        self._unify(node.test.type, builtins.TBool(),
+                    node.test.loc, None)
 
     def visit_Break(self, node):
         if not self.in_loop:
diff --git a/lit-test/compiler/inferencer/error_unify.py b/lit-test/compiler/inferencer/error_unify.py
index e81537d29..dd5c617a8 100644
--- a/lit-test/compiler/inferencer/error_unify.py
+++ b/lit-test/compiler/inferencer/error_unify.py
@@ -25,3 +25,12 @@ a = b
 
 # CHECK-L: ${LINE:+1}: error: type int(width='a) does not have an attribute 'x'
 (1).x
+
+# CHECK-L: ${LINE:+1}: error: cannot unify int(width='a) with bool
+1 if 1 else 1
+
+# CHECK-L: ${LINE:+1}: error: cannot unify int(width='a) with bool
+if 1: pass
+
+# CHECK-L: ${LINE:+1}: error: cannot unify int(width='a) with bool
+while 1: pass
diff --git a/lit-test/compiler/inferencer/gcd.py b/lit-test/compiler/inferencer/gcd.py
index e2d4b4779..87bd42716 100644
--- a/lit-test/compiler/inferencer/gcd.py
+++ b/lit-test/compiler/inferencer/gcd.py
@@ -3,7 +3,7 @@
 def _gcd(a, b):
     if a < 0:
         a = -a
-    while a:
+    while a > 0:
         c = a
         a = b % a
         b = c
diff --git a/lit-test/compiler/inferencer/unify.py b/lit-test/compiler/inferencer/unify.py
index 48681fdcb..59abd4262 100644
--- a/lit-test/compiler/inferencer/unify.py
+++ b/lit-test/compiler/inferencer/unify.py
@@ -33,8 +33,8 @@ j = []
 j += [1.0]
 # CHECK-L: j:list(elt=float)
 
-1 if a else 2
-# CHECK-L: 1:int(width='f) if a:int(width='a) else 2:int(width='f):int(width='f)
+1 if c else 2
+# CHECK-L: 1:int(width='f) if c:bool else 2:int(width='f):int(width='f)
 
 True and False
 # CHECK-L: True:bool and False:bool:bool